The United States has a new cause to defend in the miasma of the Middle East. It was when the army of the extremist movement known as the Islamic State approached the border of Kurdistan that President Barack Obama unleashed U.S. aircraft to halt the advance.

With Iraq and Syria crumbling, Iraqi Kurdistan has remained an island of stability within the roiling sea of warring Arabs. Kurdistan is a semi-autonomous region of northern Iraq that has jealously guarded its independence while Arab Iraqis descended into civil war and continuing sectarian strife.

Kurds are a nationality that has always yearned for a nation. They are spread over parts of Iraq, Iran, Turkey and Syria. They are not Arabs; they speak Kurdish. They are predominantly Sunni Muslims, but they have not been caught up by sectarian passions the way their Arab neighbors have been.

They have suffered persecution at the hand of all the nations where they live. They have carried on a protracted guerrilla war in Turkey, where their language was banned. They were subjected to mass killings, including murder by poison gas, by Saddam Hussein in Iraq. After the Gulf War ended, Saddam mounted genocidal attacks against Kurds, driving thousands of refugees into the mountains of northern Iraq, where U.S. airdrops under President George H.W. Bush helped them survive. A no-fly zone in the years that followed protected them from further attacks by Saddam.

When the U.S. drove Saddam from power, the Kurds saw their chance. Their Kurdish federation is a largely self-governing region, defended by the irregular troops known as peshmerga. They have developed a semblance of democracy, and their oil wealth allowed their economy to thrive as the rest of Iraq became enveloped by a Sunni versus Shia civil war.

The emergence of the Islamic State movement from within the Syrian civil war has changed the landscape. The weakness of the Iraqi government became apparent as Islamic State forces swept across northern Iraq, capturing Mosul, Iraq’s second largest city, and seizing sizable stores of weapons, money and important oil facilities. When the Islamic State mounted a genocidal campaign against Yazidis, Christians, Turkmen and others, it caught the world’s attention. As Yazidis took refuge in the mountains, the way the Kurds had 24 years ago, the Obama administration took note. As the Islamic State threatened Erbil, the Kurdish capital, the administration took action.

Maintaining the independence of a stable Kurdistan, where many Americans have established lucrative business ties, would seem to provide the United States a firm policy guidepost. Kurds view Americans as their lifeline and their defenders. Americans view Kurdistan as a bulwark against the chaos that has enveloped Iraq and Syria.

Kurdistan at the moment provides a haven for thousands of refugees from the onslaught of the Islamic State in Iraq. Indeed, the viciousness of the Islamic State, evident in the recorded beheading of American journalist James Foley, has made it easier for Obama to decide to target the Islamic State for air strikes. So far the American position is mainly defensive, protecting Yazidi refugees, helping Iraqis and Kurds reclaim a major hydroelectric dam, and halting the IS advance on Kurdistan.

The Islamic State is said to have as many as 17,000 well-armed fighters in Syria and Iraq. The force developed originally in opposition to Bashar Assad, the brutal dictator of Syria. But lately, there have been reports that Assad is actually helping the movement in its fight against other Syrian rebels.

The cross-currents among warring parties in Syria and Iraq make entry into that war problematic, but halting the tide of the Islamic State in Iraq, preventing genocide and defending Kurdistan are aims that justify military intervention by the United States. Certainly, Obama does not want to get dragged back into another war in Iraq. But the malevolence of the Islamic State demands a response. Sunni forces in Iraq helped the cause of the Islamic State, but in time most Iraqis, even Sunnis alienated by the Shiite government in Baghdad, are likely to see that resisting extremist barbarism has become a new imperative. The United States can help give them that time.